Earlier today, the Dow Jones Industrial Average snapped a string of ten straight days in which the index closed higher than the day before.

As a whole, the markets are very strong at the moment, with the DJIA and S+P 500 right near their all-time highs. Many investors are shovelling money hand-over-fist into the markets right now, hoping not to miss out on what seems like an endless move higher.

Former Fed Chairman Alan Greenspan weighed in on the state of the markets earlier today on CNBC, claiming that stocks are "significantly undervalued" by historical standards, and that there is no "irrational exuberance" in the markets right now.

"Irrational exuberance"?

If you've been around for a while, you'll remember that Alan Greenspan used the term "irrational exuberance" to describe the markets all the way back in December of 1996.

During a speech at the American Enterprise Institute back in late 1996, Alan Greenspan included the term "irrational exuberance" in an otherwise boring speech about the economy and stock market. Markets traded lower after Greenspan's speech, but quickly recovered. The NASDAQ would go on to quadruple in the years following Greenspan's speech before plunging after the turn of the millenium.

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If you thought that Greenspan would use the term "irrational exuberance" to describe the current juiced-up state of the markets, you would be wrong.